Power cable conductor for reducing windage



Nov. l5, 1966 J. R. McLouGHLlN 3,286,018 l POWER CABLE CONDUCTOR FORREDUCING WINDAGE Filed DeC- 24, 1964 by Q10 His /orneg United StatesPatent O 3,286,018 POWER CABLE CONDUCTOR FOR REDUCIN WINDAGE Joseph R.McLoughlin, Burnt Hills, N.Y.`, asslgnor to General Electric Company, acorporation of New York Filed Dec. 24, 1964, Ser. No. 420,977 7 Claims.(Cl. 174-42) This invention relates to electrical conductors, and. morespecifically, to electrical conductors constructed in a manner to reducewindage losses, corona lossesnand radio frequency interference thereon.v

In the transmission of high voltages over electrical power cables, someof the most frequently ocurring difficulties are the effects of windageforces and corona losses on the transmission cable, and the propagationof radio frequency interference by the cable` These difficulties haveled to numerous attempts at overcoming them individually, mostly withexpensive and often unwieldly equipment. Vibration effects caused bywinda-ge have been somewhat lessened by the hanging of weights atappropriate places along the conductor. Attempts have been made tooverc-ome corona loses by encasing the transmission cable in asurrounding sheath filled with graphite or other suitable material.Corona losses are reduced to some extent by this method but windagedifficulties are greatly increased, since one of the worst shapes forwindage purposes is the circular cable shape, and now this circularshape has been increased in diameter and therefore the windagedifliculties .are accordingly increased. There has been very little workalonng the line of shaping the conductor itself so that windage, coronalosses and radio frequency interference are overcome at the same timewhen the cable is originally installed. The need then arises for anelectrical conductor for a transmission cable that is constructed' toovercome windage losses,

corona losses and radio frequency interference thereon.

In my copending application entitled Covering for Power Line ConductorsTo Reduce, Windage, Corona Loss and Radio Frequency InterferenceffSerial No. 421,017,l I have disclosed apparatus that is added to acircular power conductor or other structure for overcoming windage,rcorona losses and radio frequency interference thereon. In the `presentapplication, I cover` the use of a conductor that is designed in itselfto overcome 'windage effects, radio frequency interference and' coronalosses thereon.

My invention envisionsan electrical conductor having an overallaerodynamic air foil shape that induces streamlined flow around itsVsurface for reducing windage losses and also having a conductingsurfacefor reducing radio frequency interference and corona lossesthereon.

The chief object of my invention is the provision of an electricalconductor having an overall air foil shape to promote even streamlinedflow overits surface to reduce windage losses thereon.

Another object of my invention is the provision ofv an electricalconductor which has an air foil shapel to reduce windage-losses andwhich has conducting means forv reducing corona losses thereon. fAnother object of my invention is the provision-of an electricalconductor having an aerodynamic air foil shape to reduce windage lossesand having a coating of av semiconductor to provide means for overcomingcorona losses and radio frequency interference thereon.

K nother object of my invention is the provision of an electricalconductor having an air foil shape for overcom-ing windage losses andhaving a conducting surface that increases the effective circumferenceof the conduct-or to substantially reduce corona losses and radiofrequency interference thereon.

A' further object of my invention is' the provision of an 3,286,0 18Patented Nov. 15, 1966 lCC 2 electrical conductor shaped to maximizetorsional rigidity that is combined with a foam material to form anoverall streamlined shape to promote even nonturbulent flow around itssurface for reducing windage and corona losses thereon These and otherobje-cts of my invention will be more readily perceived from thedescription which follows.

One of the features of my invention is a highly etlicient electricaltransmission cable having a flat aerodynamic air foil shape thatpromotes streamlined nonturbulent fiow over its surface to substantiallyreduce windage losses, and which surface is also a conductor orsemiconductor to increase the effective circumference of the cable toovercome corona losses and radio frequency interference thereon.

The attached drawing illustrates preferred embodiments of my inventionin which:

FIGURE 1 is a cross-sectional view of the conductor of my invention;

FIGURE 2 is a cross-sectional view of a modification of the conductor ofFIGURE 1;

FIGURE 3 is a cross-sectional View of a further modication of theconductor of FIGURE 1; and

FIGURE 4 is -a cross-sectional view of a modilication of the conductorof FIGURE 3.

In FIGURE l there is shown a cross-sectional view of an air foil shapedconductor embodying my invention. The construction includes electricalconductor 2 which is constructed of copper, aluminum or any othermaterial generally used for the conduction of electrical current.Conductor 2 has an air foil shape having a cross-sectional length whichis horizontal and much greater than its crosssectional. width. Thisshape generally comprises two rounded ends 4 interconnected by suitablemeans to form this overall streamlined shape. In FIGURE l such meanscomprise center member 5 which provides electrical conductivity andstructural and torsional rigidity between ends 4. Member 5 may beintegral with ends 4 or alternatively separately secured thereto. Thecross-sectional current carrying area of conductor 2 is then quite largesince ends 4 and center members 5 all carry current and, therefore, highcurrents can be effectively carried bythe conductor. Light weightmaterial 6 is placed on either side of center bar 5 to fill areas 8between the ends 4 of the conductor and center bar 5, toL form a smoothsurface so that air flows in 4a streamline manner around conductor 2.This smooth outer surface is shown as being straight but it. might alsobe slightly convex outward. Light weight material 6 may comprise a foammaterial such as polystyrene, polyethylene, polypropylene, epoxy,rubber, urethane, polyvinyl chloride foams, or any suitable foamymaterial that is light in weight relative to the cable and easyinstalled. Connecting end tips 7 of conductor ends 4 there is a thinlayer 10 of a semiconducting material or conducting material, comprisingeither a coating on the outer surface of foam 6, or a thin jacket overit, Vto aid in effectively reducing corona loss and radio frequencypropagation on conductor 2, as will subsequently bel discussed.

In operation, the cable is installed in a horizontal position withcenter bar 5, which is coincidental with the cross-sectional axis ofsymmetry of the conductor, parallelk to the earth. Since wind generallyblows in a horizontal plane, or at slight angles thereto, the force ofthe wind vimpinges on either end 4 of the electrical conductor. Ends 4are rounded in an aerodynamic manner approximating an air foil shape sothat air currents flow evenly in a stre-amline manner over surfaces 9and either end 4 to minimize turbulent vertical flow around and behindconductor 2 and thereby substantially reduce the windage drag forcethereon. It is important to note that for effective operation of an airfoil, the streamlined shape 3 must be the last surface the air flowsover. Therefore, regardless of the direction of the' wind, both ends'4yare shaped in the same aerodynamic manner so that the air flow over theconductor always terminates its flow in a streamlined manner over eitherend 4. Conductor 2 ybecause of its elongated cross-section, has lowwindage losses, whereas an equivalent circular conductor would havesubstantially greater losses due to turbulence and pressure gradientsaround its circumference. Thus, conductor 2 is susbtantially larger thana circular conductor having an equivalent cross-sectional con-ductingarea, but nevertheless conductor 2 has far less windage drag effectthereon (probably on the order of 20 percent of the windage of acircular conductor of the same cross-sectional conducting area) becauseof its streamlined construction.

By the employment Iof a thin layer of semiconducting or conductingmaterial on the outside of foam material 6, the effective circumferenceof conductor 2 f or corona reduction purposes becomes the outercircumference including this coating layer 10 and ends 4 of theconductor.

This effective conductor circumference is thenfar greater than it wouldbe for a circular conductor of the same cross-sectional conducting area.Corona losses and the subsequent luminescent ionization of the airsurrounding the conductor, which are inversely proportional to theeffective perimeter of the conductor are thus reduced substantially, bythis increase in perimeter of the conductor. The effectivecircumference` of thevconductor is then increased in a m-anner thatavoids sharp bends and f small radii, which are points of excessivecorona discharge. When thin skin 10 is made semiconductive, with theproper resistivity, radio frequency interference is substantiallyreduced by the attenuation lof radio frequency waves along theconductor.

This radio frequency interference reduction only takes place with asemiconducting 'coating but the corona loss reduction function takesplace effectively with either a serniconductingA or a conductingcoating.

It is also noted that the swing angle of the cable with this conductorshape is also substantially reduced by virtue of negative lift orpressure downward as the conductor swings out to thereby reduce theangle to which it swings. It is also noted that a negative angle ofattack with respect to the wind direction also decreases this swingangle.

In FIGURE 2 there is shown a modification of the device of FIGURE 1whereby end sections 20 of conduc- 'tor 19 are semicircular incross-sectional area, thereby providing for a greater conducting areawithin the same total cross-sectional area as FIGURE 1.` Because ofthese ends 20, the polar moment of inertia of the conductor issubstantially increased with only a small increase in weight thereof.Such an increase in the polar moment of inertia helps to preventtwisting of the conductor caused by the asymmetry of wind forces on theconductor. As with FIGURE l, FIGURE 2 `has filler 22 of a light weightmaterial and skin 24 of a semiconductor or conductor. The operation ofFIGURE 2 is the same as that of FIGURE 1 in reducing Windage, coronaloss and radio frequency interference thereon.'v

In FIGURE 3 there is shown a hollow conductor 30 having the same airfoil cross-sectional shape as that of v ductor hollow, the outerperimeter is increased,v over -a circular conductor,while'thefcross-sectional conducting area Iand weight are keptconstant.yThis, of course, results lin an effective outside circumference that issubstantially larger than a circular conductor of the samecross-sectional larea and as previously mentioned, the

greater the eifective circumference of the conductor, the

7 0f .p h

.corona loss and radio frequency interference on electrical Atransmission lines comprising less the corona loss. A simple method isthen provided effects and high resistance to torsion.

It will be appreciated that the overall shape of conductor 30 -is astreamlined one since it has the same shape as the overall member ofvFIGURE l or 2. Ends 34 which come into contact with the wind as it isleaving conductor 30 are aerodynamicallyy curved as is all of member 30to facilitate even streamline flow of air Acurrents around and behindits surface. Turbulence that would be inherent in a circular conductorwhether the rcircular conductor were hollow or solid is thus avoided.Swing angles are also substantially reduced because of the reduction ofwindage losses. It is also noted that transportation of conductor 30 isrelatively easy because land its counterpart on the otherside (notillustrated) form a brace on each end of conductor 41 as it is beingformed; Braces 42 also provide added torsional stiffness to the entireconductor lwhen it is employed in a high windage field. The thin coating43 and the rounded ends v44 are employed in the same manner as the modeof FIGURES l and 2v for reduction of Windage, corona losses andradioffrequency interference thereon.

It is noted that, with the modes of the conductor I have 4illustratedand described, thermal transfer by convection or radiation, is easilyaccomplished because of the large areas of the conducting surface thatare exposed to the atmosphere. In FIGURE l, ends 4, FIGURE 2,

'ends 20, and in FIGURE 4, ends 44, have their outer surfaces completelyexposed to the atmosphere .and in FIGURE 3 the entire outer surface ofthe conductor is exposed to the atmosphere. There will be no dicultywith heating on the hollow conductor of FIGURE 3 since the conductoritself is a good thermal conductor and therefore dissipates the he-atthrough the conductor walls to the outside ambient air. l

It is also noted that, with the various modes of my 'invention becauseof the large polar moments of inertia,

a high degree of torsional stiffness of the conductors to preventtwisting is achieved.

. Typical coatings that are used for the outside skin 10 in FIGURE l, 24in FIGURE 2, or 43 in FIGURE 4 are phenolic resin, plyethylene,polyurethane, polyvinyl chloride, rubber or other polymers, which maybear carbon black or metal particles to provide a semiconductingsurface. This skin lmay either be a coating or a separate thin sleevethat is secured to the main member. It is now apparent that my inventionattains the objectives setforth. Apparatus embodying the invention issturdy in construction and well adapted for use in con- .Junctron withvarious environments. Windage, corona loss and radio frequencyinterference are substantially reduced on power cables while-maintaining torsional rigidity therein.

Specic embodiments of my invention have been illustrated buttheinvention is not limited thereto since many modifications may be made byone skilled in the art and the appended claims are intended to cover allsuch modiinvention.

ications .as fall within the true spirit .and scope of my What I claimas new and'desire to secure by Letters Patent of the United States is:

1i. An apparatus for reducing the effects of Windage,

an air foil shaped conductor having a cross-sectional length greaterthan its cross-sectional height, 4 Vatrailing edge at one end of saidcross-sectional length of said conductor positioned on the opposite sideof the conductor from where the wind is coming and with thecross-sectional length of said conductor being in a plane parallel tothe direction of the wind for the wind to pass smoothly around the'conductor in a streamlined manner to reduce the effects of windagethereon, and

means for providing a large conducting circumference on said conductorfor reducing corona loss and radio frequency interference thereon.

2. An apparatus for reducing the effects of windage and corona loss onelectrical transmission lines comprising an air foil shaped conductorhaving a cross-sectional length greater than its cross-sectional height,

trailing edges on said conductor at both ends of said cross-sectionallength so that one of said trailing edges is always positioned on theopposite side of the conductor from Where the wind is coming, and withthe cross-sectional length of said conductor being in `a plane parallelto the direction of the wind for the wind to pass smoothly around theconductor in a streamlined manner to reduce the effects of windagethereon,

a central member interconnecting said trailing edges to providetorsional rigidity to said conductor,

conducting means interconnecting said edges for providing a large,smooth conducting circumference for reducing corona loss on theconductor.

3. An apparatus for reducing the effects of windage, corona loss andradio frequency interference on electrical tnansmission lines comprisingau air foil shaped conductor having a cross-sectional length greaterthan its cross-sectional height,

trailing edges on said conductor at both ends of Said cross-sectionallength, so that one of said trailing edges is 4always positioned on theopposite side of the conductor from where the wind is coming, and withthe cross-sectional length of said conductor being in a plane parallelto the direction of the wind, for the wind to pass smoothly around theconductor in a streamlined manner to Ireduce the effects of windagethereon,

a central member interconnecting said trailing edges to providetorsional rigidity to said conductor,

semi-conducting means interconnecting said edges for providing a large,smooth conducting circumference for reducing corona loss and radiofrequency interference on the conductor,

filler means between said central member and said semi-conducting meansto provide support thereto.

4. An apparatus for reducing the effects of windage,

corona loss and radio frequency interference on electrical transmissionlines as defined in claim 3 where said edges are semi-circular incross-sectional area.

5. An apparatus for reducing the effects of windage, corona loss andradio frequency interference on electrical transmission lines comprisingan air foil shaped conductor having a cross-sectional length greaterthan is cross-sectional height,

U-shaped trailing edges on said conductor at both ends of saidcross-sectional length, so that one of said trailing edges is alwayspositioned on the opposite Side of the conductor from where the wind iscoming, and with the cross-sectional length of said conductor being in aplane parallel to the direction of the wind, for the wind to passsmoothly around the conductor in a streamlined manner to reduce theeffects of windage thereon,

a central member interconnecting said trailing edges to providetorsional rigidity to said conductor,

semi-conducting means interconnecting said edges for providing a largesmooth conducting circumference for reducing corona loss and radiofrequency interference on the conductor,

filler means between said central member and said semi-conducting meansto provide support thereto,

rods placed within the U-shaped edges of the conductor to aid inproviding torsional rigidity thereto.

6. An apparatus for reducing the effects of windage, corona loss andradio frequency interference on electrical transmission lines as setforth in claim 3 in which said edges are a semicircular Segment in crosssection area to prevent twist.

7. An apparatus for reducing the effects of windage, corona loss andradio frequency interference on electrical transmission lines as setforth in claim 5 in which said central member is attached to saidU-shaped trailing edges at the bottom of the U and the stiffening rodsare fastened into the open end of the U to provide a smooth exteriorsurface and prevent twist.

References Cited by the Examiner UNITED STATES PATENTS 689,615 12/1901Heyl-Dia 174-133 X 2,057,266 10/1936 Rippere 174-133 2,060,859 11/1936Plym 174-1335( 3,121,770 2/1964 Dany@ 174-42 FOREIGN PATENTS 877,5889/1942 France.

558,084 2/1953 Italy.

LEWIS H. MYERS, Primary Examiner. G. GOLDBERG, Assistant Examiner.

2. AN APPARATUS FOR REDUCING THE EFFECTS OF WINDAGE AND CORONA LOSS ONELECTRICAL TRANSMISSION LINES COMPRISING AN AIR FOIL SHAPED CONDUCTORHAVING A CROSS-SECTIONAL LENGTH GREATER THAN ITS CROSS-SECTIONAL HEIGHT,TRAILING EDGES ON SAID CONDUCTOR AT BOTH ENDS OF SAID CROSS-SECTIONALLENGTH SO THAT ONE OF SAID TRAILING EDGES IS ALWAYS POSITIONED ON THEOPPOSITE SIDE OF THE CONDUCTOR FROM WHERE THE WIND IS COMING, AND WITHTHE CROSS-SECTIONAL LENGTH OF SAID CONDUCTOR BEING IN A PLANE PARALLELTO THE DIRECTION OF THE WIND FOR THE WIND TO PASS SMOOTHLY AROUND THECONDUCTOR IN A STREAMLINED MANNER TO REDUCE THE EFFECTS OF WINDAGETHEREON, CENTRAL MEMBER INTERCONNECTING SAID TRAILING EDGES TO PROVIDETORSIONAL RIGIDITY TO SAID CONDUCTOR, CONDUCTING MEANS INTERCONNECTINGSAID EDGES FOR PROVIDING A LARGE, SMOOTH CONDUCTING CIRCUMFERENCE FORREDUCING CORONA LOSS ON THE CONDUCTOR.